Overlay proofs comprising precolored and toned images

ABSTRACT

Provided is a multilayer, multicolor overlay proof comprising at least one precolored overlay image and at least one toned overlay image, as well as a process for preparing such an overlay proof.

This is a division of application Ser. No. 07/475,056, filed Feb. 5,1990, now U.S. Pat. No. 5,001,037.

FIELD OF THE INVENTION

This invention relates to processes for image reproduction. Moreparticularly, it relates to processes in which overlay images areprepared using clear, tonable photosensitive elements and, further, toprocesses in which these toned overlay images are combined with overlayimages prepared from precolored elements.

BACKGROUND OF THE INVENTION

Photosensitive elements which can be used in image-reproductionprocesses are well-known in the graphics arts industry. Such elementsare usually exposed to actinic radiation through an image-bearingtransparency, such as a color separation transparency, to produce animage which is either a positive or a negative with respect to thetransparency used. Positive-working elements produce an image which is aduplicate of the transparency through which they are exposed. That is,the colored regions of the transparency are also colored in the imagedelement and the uncolored regions in the transparency are uncolored inthe imaged element. Negative-working elements produce an image that isthe reverse of the transparency through which they are exposed. That is,the colored regions of the transparency are uncolored in the imagedelement and the uncolored regions in the transparency are colored in theimaged element. Ordinarily, a positive-working element is exposedthrough a positive transparency to produce a positive image, and anegative-working element is exposed using a negative transparency toproduce a positive image. After imagewise exposure, the photosensitiveelements may be developed by washout of soluble image areas, by peelingapart, by toning with a colorant, or combinations of these techniques.

Such photosensitive elements are widely used in pre-press or off-presscolor proofing systems to simulate the images reproduced by printing.Pre-press color proofs include overlay systems and surprint, or singlesheet, systems. In an overlay proof, each color is on a separatetransparent sheet. The individual films are assembled in register andviewed as a composite against an appropriate background, e.g., an opaquereflective white sheet. In an overlay system the individual coloredelements remain separable and can be combined or viewed separately.

Conventional overlay proofing films are precolored by theirmanufacturers. Thus, in the preparation of overlay images, the operatoris limited to those colors provided by the manufacturer. Because of thecost of manufacture, inventory, and distribution, necessarily only alimited range of colors will be available. A number of commercialoverlay proofing systems are described in detail in Principles of ColorProofing, by Michael H. Bruno, GAMA Communications, Salem, NH, 1986,Chapter V, "Off-Press Color Proofing Systems--Overlay", pp 133-146, theteachings of which are incorporated by reference.

The process of the invention permits preparation of overlay images withspecialty, i.e., non-standard, colors from a non-colored, tonableelement. The operator can use precolored overlay films to prepare imagesrequiring standard colors and use the non-colored, tonable element toprepare toned images requiring specialty colors. These precolored andtoned images can then be combined to form a multilayer, multicoloroverlay proof consisting of toned and precolored images. Because theoperator can mix the toners supplied by the manufacturer as desired,toned images with an almost unlimited variety of colors can be prepared.Instead of providing many specialty films, the manufacturer only has tosupply precolored films in a limited number of standard colors inaddition to a single non-colored, tonable element.

There is a need for such a process by which both precolored and tonedoverlay images can be prepared from a single set of separationtransparencies and combined to form a single, multilayer, multicoloroverlay proof.

For such a process to be practical, both the precolored films and thenon-colored, tonable element must work in the same sense, i.e., bothmust be either positive or negative working. For example, if theprecolored film were negative working and the non-colored, tonableelement were positive working, it would be necessary to provide negativeseparation transparencies to prepare the precolored overlay images andpositive separation transparencies to prepare the toned overlay images.

It is also essential that the toned image have the correct left to rightorientation when viewed with the toned image down, i.e., away from theobserver, and the support up, i.e., facing the observer. Thisorientation is required to protect the image during normal storage,handling, and use. Therefore, the process must produce a toned imagewhich has the correct left to right orientation when viewed with thetoned image down.

Further, such a process must produce both precolored and toned imageswhich have the same right to left orientation as the image beingreproduced. None of the images can be a mirror image of the originalimage.

SUMMARY OF THE INVENTION

The invention provides a process for preparing a multilayer, multicoloroverlay proof comprising at least one precolored overlay image and atleast one toned overlay image, comprising the steps of:

(A) providing at least two different conventional color separationtransparencies of the image to be reproduced, all of which are eitherpositive or negative, and each comprising an emulsion image on a base;

(B) providing at least one precolored photosensitive overlay element andat least one non-colored, tonable photosensitive overlay element, all ofwhich are either positive or negative working as required by saidseparation transparencies;

(C) exposing a precolored photosensitive overlay element to actinicradiation through its corresponding color separation transparency withthe emulsion side of the transparency down, and developing to provide aprecolored overlay image;

(D) exposing a non-colored, tonable photosensitive overlay elementthrough a different color separation transparency with the emulsion sideof the transparency up, developing and toning with a correspondinglycolored toner to provide a toned overlay image, and inverting said tonedoverlay image to obtain the correct left to right orientation; and

(E) assembling in register, said developed precolored overlay image inexposure position and said developed toned overlay image in invertedposition to form a multicolored, multilayer overlay proof with correctleft to right orientation; wherein steps (C) and (D) may be carried outin either order.

Optionally, steps (C) and/or (D) may be repeated as many times asdesired with different color separation transparencies of the image tobe reproduced to produce a plurality of different color overlay imageswhich are stacked in register to produce a multilayer, multicoloroverlay proof.

In a preferred embodiment of this invention, the non-colored, tonablephotosensitive element comprises a photosensitive layer, an elastomericlayer, and a transparent support. In a more preferred embodiment of thisinvention the non-colored, tonable photosensitive element(s) is apeel-apart photosensitive element comprising a coversheet, aphotohardenable layer, an elastomeric layer, and a support. In anothermore preferred embodiment of this invention the non-colored, tonablephotosensitive element(s) is a solvent-processible element comprising asolvent-processible photosensitive layer, an elastomeric layer, and asupport. In an even more preferred embodiment of this invention, thenon-colored, tonable photosensitive element(s) is a negative-working,peel-apart photosensitive element comprising a coversheet; aphotohardenable layer consisting essentially of a monomer, a binder, anda photoinitiator system; an elastomeric layer; and a support.

DETAILED DESCRIPTION OF THE INVENTION Exposure/Image Formation

In using non-colored, tonable photosensitive elements to prepare singlecolor, toned overlay images from conventional color separationtransparencies, each element is exposed to actinic radiation through atransparency. If the transparency is a negative, a negative workingelement must be used. If the transparency is a positive, a positiveworking element must be used.

The transparency comprises an imaged emulsion layer on a base. In aconventional exposure, using a conventional pre-colored, overlayproofing element, the transparency is orientated so that the emulsionside of the transparency is in contact with the photosensitive elementand the base faces the source of actinic radiation, i.e., the emulsionside is "down". This is the standard exposure procedure, especially withrespect to halftone reproduction processes, because mounting thetransparency with the emulsion surface not in contact with thephotosensitive element is known to alter the image by either dotsharpening and/or dot gain. See, Bruno, Principles of Color Proofing,p.63. Conventional transparencies have the correct left to rightorientation with respect to the original when viewed with the emulsionside facing away from the viewer. When a photosensitive element isexposed through such a transparency with the emulsion side of thetransparency "down", the photosensitive element will also have thecorrect left to right orientation when viewed as it was mounted duringexposure, i.e., "exposure position".

However, in the process of this invention, the toned overlay image(s) isexposed with the transparency in the inverted position. The transparencyis turned over, or inverted, i.e., the emulsion side is "up", so thatthe emulsion side of the separation transparency faces the source ofactinic radiation and the base is in contact with the non-colored,tonable element. The exposed element is then processed and toned, usinga toner which corresponds to the color separation transparency used, toproduce a toned overlay image. The toned image element is then inverted,i.e., turned over, so that it has the correct left to right orientation.The inversion step also orients the overlay image so that the support isup, i.e., facing the observer, and the toned image down, away from theobserver. The overlay image should have the toned image down to protectit during storage, handling, and use.

To form additional toned, single-color overlay images, this sequence ofsteps may be repeated using additional non-colored, tonable elementscombined with different separation transparencies and theircorresponding toners.

The precolored photosensitive element, that is, the conventionalprecolored overlay proofing film, is exposed and processed in theconventional fashion. Actual processing steps will differ depending,e.g., on the structure and chemistry of the element. During exposure theemulsion side of the separation transparency is in contact with theelement and the side which does not bear the emulsion faces the sourceof actinic radiation. This produces a conventional single-color,precolored, overlay image. To form additional precolored single-coloroverlay images, this sequence of steps may be repeated with differentseparation transparencies and their corresponding precoloredphotosensitive elements.

To prepare a multilayer, multicolor overlay proof, the variousprecolored overlay images and inverted toned overlay images are stackedin register on top of an appropriate receptor. The conventionalprecolored overlay images are stacked in "exposure position" and thetoned overlay images are stacked in the inverted position, so that allof the images have the correct left to right orientation.

Non-colored, Tonable Photosensitive Elements

The non-colored, tonable photosensitive element may be any of numerouselements known in the art. One type of element comprises aphotosensitive layer and a support. Another type comprises, in order, aphotosensitive layer, an elastomeric layer, and a support.

Two-Layer Elements

Elements of this type comprise a photosensitive layer and a support.Exposure to actinic radiation changes the photosensitive layer so thatit either accepts toner, in the case of negative-working elements, ordoes not accept toner, in the case of positive-working elements.

Conventional positive-working non-colored, tonable photosensitiveelements are disclosed in Chu, U.S. Pat. No. 3,649,268. These elementscomprise a photohardenable layer and a removable support. Exposureraises the tack temperature of the photohardenable layer so that tonerdoes not adhere to exposed areas. For use in this invention, the supportneed not be removable. It must, however, be optically transparent sinceit becomes the image carrier for the overlay image. This is true for thesupport or image carrier of any overlay element whether precolored ornoncolored used in this invention.

Negative-working non-colored, tonable photosensitive elements aredisclosed in Abele and Grossa, U.S. Pat. No. 4,243,741. These elementscomprise a support bearing a layer of a photosensitive compositioncomprising a thermoplastic binder, at least one dihydropyridine compoundand at least one hexaarylbiimidazole (HABI). Exposure changes theexposed areas so they accept toner.

Multi-Layer Elements

Elements of this type comprise, in order, a photosensitive layer, anelastomeric layer, and a support. In this type of element, the physicalproperties of the photosensitive layer are changed on exposure so thateither the exposed or the unexposed areas can be removed duringprocessing, uncovering the tonable elastomeric layer.

If the exposed areas are removed, the element is negative working withrespect to the transparency used for exposure. If the unexposed areasare removed, the element is positive working with respect to thetransparency used for exposure. The uncovered elastomeric layer acceptstoner during the toning step. The excess toner is removed from theelement, leaving an image consisting of the imaged and processedphotosensitive layer, toned elastomeric layer, and support. Optionally,and depending on the nature of the element, the residual photosensitivelayer may be removed from the element by further processing as describedin Spechler, U.S. Pat. No. 4,376,158. The support provides dimensionalstability to the toned elastomeric layer.

Peel-Apart, Tonable Photosensitive Elements

A peel-apart, tonable photosensitive element useful in the process ofthe invention comprises a coversheet, a photosensitive layer, anelastomeric layer, and a support. In these elements the photosensitivelayer is a photohardenable layer, that is, one which isphotopolymerizable, photocrosslinkable, and/or photodimerizable.

Negative Working Peel-Apart Elements

Conventional peel-apart photosensitive elements are negative working,that is, when the coversheet is peeled off, the exposed areas areremoved with the coversheet, thereby uncovering the tonable elastomericlayer. Such elements are disclosed in Cohen and Fan, U.S. Pat. Nos.4,247,619 and 4,282,308.

Photohardenable Layer

The photohardenable layer, which is the sole photosensitive layer of thepeel-apart element, is one whose adhesive relationship vis-a-vis thecoversheet and the elastomeric layer is altered by exposure to actinicradiation. Before exposure, the photohardenable layer adheres morestrongly to the elastomeric layer than to the coversheet. If theunexposed element is peeled apart, the photohardenable layer remains onthe elastomeric layer. After imagewise exposure of the element with thecoversheet in place, the exposed areas of the photohardenable layeradhere more strongly to the coversheet than to the elastomeric layer andare removed with the coversheet.

Monomers/Binders

The preferred photohardenable compositions are photopolymerizable, andcomprise a macromolecular organic polymeric binder, an additionpolymerizable ethylenically unsaturated monomer, and an initiator orinitiator system. The monomer has at least one and preferably two ormore terminal ethylenically unsaturated groups capable of free-radicalinitiated, chain propagated, addition polymerization, and preferably hassome degree of polarity. In addition, the monomer must be compatiblewith the binder and substantially nondiffusible in the elastomericlayer. Useful monomers include epoxy monomers containing ethylenicunsaturation, such as are disclosed in U.S. Pat. No. 3,661,576.Preferred monomers are the diacrylate and dimethacrylate esters of theepichlorohydrin adduct of bis-phenol A. Suitable binders includepolymers of methyl acrylate, methyl methacrylate, and copolymersthereof. A preferred binder is poly(methyl methacrylate).

Initiator Systems

The initiator system comprises one or more compounds which directlyfurnish free-radicals when activated by actinic radiation. It can alsocomprise a plurality of compounds, one of which yields the free-radicalsafter having been caused to do so by another compound, or sensitizer,which has been activated by the radiation.

Numerous conventional initiator systems may be used to initiatephotopolymerization provided they (1) are compatible with the otheringredients of the system, (2) do not alter the unique relationshipbetween the coversheet, the elastomeric layer, and the exposed andunexposed photohardenable layer required for the operation of thepeel-apart element, and (3) do not impart unwanted color to the finalimage.

Preferred initiator systems are 2,4,5-triphenylimidazolyl dimers incombination with chain transfer agents, or hydrogen donors, and mixturesthereof. Preferred HABI's (hexaarylbisimidazoles) are2-o-chlorosubstituted hexaphenylbisimidazoles in which the otherpositions on the phenyl radicals are unsubstituted or substituted withchloro, methyl or methoxy. The most preferred initiator is o-Cl-HABI,i.e., 1,1'-biimidazole, 2,2'-bis(o-chlorophenyl)-4,4,'5,5'-tetraphenyl-.A preferred sensitizer is 7-diethylamino-4-methylcoumarin.

Hydrogen donor compounds useful as chain transfer agents in thephotopolymer compositions include: 2-mercaptobenzoxazole,2-mercaptobenzothiazole, 4-methyl-4H-1,2,4,triazole-3-thiol, and thelike. A preferred hydrogen donor is 2-mercaptobenzoxazole.

Other Ingredients

The photohardenable layer may also contain other ingredients which areconventional components used in photohardenable systems subject to theconditions that they (1) must be compatible with the other ingredientspresent in the photohardenable layer, (2) do not alter the uniquerelationship between the elastomeric layer, the unexposed and exposedphotohardenable layer, and the coversheet required by the peel-apartphotosensitive element, and (3) do not impart unwanted color to thefinal image. Such components may include stabilizers, antihalationagents, optical brightening agents, release agents, surfactants, coatingaids, and plasticizers.

Normally a conventional thermal polymerization inhibitor will be presentto increase stability in the storage of the photohardenable composition.The dinitroso dimers described in Pazos, U.S. Pat. No. 4,168,982, mayalso be useful. Since monomers generally contain thermal polymerizationinhibitors added by their manufacturers, it is frequently unnecessary toadd additional inhibitor.

Nonionic surfactants may be added to the photohardenable layer ascoating aids. Preferred coating aids are polyethylene oxide, such asPolyox® WSRN 3000, and fluorinated nonionic surfactants, such asFluorad® FC-430.

By the incorporation of optical brightening agents into thephotohardenable layer, the image record is produced free from distortiondue to halation effects. Particularly useful optical brighteners are2-(stibyl-4")-(naphtho-1',2',4,5)-1,2,3-triazol-2"-sulfonic acid phenylester and7-(4'-chloro-6'-diethylamino-1',3',5'-triazine-4'-yl)amino-3-phenylcoumarin. Useful ultraviolet radiation absorbing materials andbrighteners are disclosed in U.S. Pat. No. 3,854,950.

Composition

The binder/monomer ratio may vary widely but in general should be about3:1 to 1:3. The monomer should be compatible with, and may be a solventfor, and/or have a plasticizing action on the binder. The proportions ofmonomer and binder are made in accordance with the requirements ofselective photoadhesion and hardness. In order to provide a suitablehardness, the monomer concentration is normally kept low so that thephotohardenable layer will be sufficiently hard and nontacky. Theamounts of ingredients will generally be within the following percentageranges, based on total weight of the photohardenable layer: monomer,5-60%, preferably 15-50%; initiator system 0.1% to 10%, preferred 1-5%;binder, 25-75%, preferably 45-65%; other ingredients 0-5%, preferably0.5-5%.

Elastomeric Layer

The elastomeric layer is a tacky or slightly soft, deformable material.For an element with good aging stability, suitable materials for theelastomeric layer should restrain monomer diffusion from thephotohardenable layer into the elastomeric layer. In addition, thesematerials must be nonmigratory into the photohardenable layer. Preferredmaterials are elastomeric polymers and mixtures thereof, which areinherently tacky at ambient temperatures. Especially preferred materialsfor the elastomeric layer are polymers of butadiene or isoprene andrandom, teleblock and block copolymers of butadiene or isoprenecopolymerized with styrene.

Coversheet

The non-colored, tonable peel-apart photosensitive elements have acoversheet which is strippable, i.e., removable by peeling it apart fromthe rest of the element. The adhesive relationship of the coversheet tothe photohardenable layer is such that, after the photohardenable layerhas been exposed to actinic radiation, the exposed (i.e., polymerized)areas of the photohardenable layer adhere more strongly to thecoversheet than to the elastomeric layer and are removed with thecoversheet. The unexposed (i.e., unpolymerized) areas of thephotohardenable layer adhere more strongly to the elastomeric layer thanto the coversheet and remain on the elastomeric layer.

The coversheet must be transparent to actinic radiation sinceirradiation is carried out through the coversheet. Preferred materialsfor the coversheet are polymeric films, particularly polyethyleneterephthalate.

In order to make the exposed areas of the photohardenable layer adherebetter to the coversheet, the surface of the coversheet may be modified;for example, the topography may be altered and the polarity increased bya surface treatment such as electrostatic discharge or flame treatment.Photosensitive elements comprising electrostatic discharge treatedpolyethylene terephthalate film are disclosed in Buzzell, U.S. Pat. No.4,356,253. Flame treatment of the film also will provide goodphotoadhesion. An air-propane flame may be used.

The coversheet should be thick enough so that electrostatic discharge orflame treatment will not injure it and so that it may be strippedwithout tearing. While the thickness may be varied over a wide range,films having a thickness of about 0.5-3.0 mil (13-75 micrometer),preferably 0.5-2.0 mil (13-50 micrometer) can be used. Thinnercoversheets produce halftone dots of good roundness with sharp edges. Ingeneral, a rapid rate of coversheet stripping produces better imagequality.

Support

The elastomeric layer is present on a support. In conventionalnon-colored photosensitive elements the support is releasable so that itmay be removed as each successive exposed, processed, and toned elementbecomes part of a surprint proof. For use in a surprint, the supportneed not be transparent since it does not become part of the finalimage.

In contrast, in all of the tonable elements used in the processes ofthis invention the support becomes the carrier for the final overlayimage. Therefore, it need not be releasable from the elastomeric layer.It must, however, be transparent and must of be of sufficient thicknessto provide dimensional stability to the toned elastomeric layer duringprocessing, toning, and ordinary use.

The support may be any suitably transparent film which has the necessarystiffness and dimensional stability and which exhibits proper adhesionto the elastomeric layer. Clear polyethylene terephthalate film ispreferred. While the thickness may be varied over a wide range, filmshaving a thickness of about 2-3 mil (50-75 micrometer) are preferred.

Manufacture

The photosensitive element may be prepared using conventional coatingtechniques. The photohardenable layer is coated onto the coversheet.After the solvent has evaporated, a release film, such as polyethylene,may be placed over the coating to protect the photohardenable layeruntil the rest of the element is formed. The elastomeric layer is coatedover the photohardenable layer. If a release film is present on thephotohardenable layer, it must be stripped off before the elastomericlayer is coated. After the solvent has evaporated, the support islaminated to the surface of the elastomeric layer. The solvent for theelastomeric layer should not have any solubilizing or deleterious effecton photohardenable layer.

Alternatively, the photohardenable layer may be coated onto thecoversheet and the elastomeric layer coated onto the support. Thephotohardenable layer and the elastomeric layer are laminated togetherunder pressure at room temperature or elevated temperature.

The element may also be prepared using conventional multilayer coatingtechniques. The photohardenable layer and the elastomeric layer may becoated simultaneously onto the coversheet, and the support laminated tothe elastomeric layer.

The photohardenable layer is prepared by mixing the ingredients of thesystem in a suitable solvent, such as dichloromethane, usually in theweight ratio of about 15:85 to 25:75 (solids to solvent), coating ontothe coversheet, and evaporating the solvent. Coating should be uniform.A coating weight of about 35-40 mg/dm², generally providing a drythickness of about 3.5 to 4.0 microns, is preferred.

Any suitable solvent may be used to coat the elastomeric layer. When theelastomeric layer and photohardenable layer are coated simultaneously,the solvents must not cause significant migration of the componentsbetween the two layers. Coatings should be uniform and typically have athickness of 3 to 15 microns, preferably 7 to 12 microns, when dry. Drycoating weight will be about 30 to 200 mg/dm², preferably 70 to 120mg/dm².

Positive Working Peel-Apart Elements

Conventional peel-apart, tonable photosensitive elements are negativeworking. However, they may also be made positive working by appropriatemodification in composition and/or process of use.

Positive working, peel-apart photosensitive elements are disclosed inCohen and Fan, U.S. Pat. No. 4,304,839. The binders used in theseelements were; a chlorinated rubber, a chlorinated rubber/poly(methylmethacrylate) mixture, and a 3:41:48:9acrylonitrile/styrene/butadiene/methyl methacrylate co-polymer.

A positive working, peel-apart photosensitive element is described inco-assigned U.S. Pat. No. 07/318,586, filed Mar. 3, 1989. This elementcomprises, in order, a coversheet; a photorelease layer, consistingessentially of a solid, oxyethylene homopolymer of the formula, H(OCH₂CH₂)_(n) OH, with a molecular weight greater than about 3,000; aphotohardenable layer; an elastomeric layer; and a support. Thecomposition of the photohardenable and elastomeric layers is asdescribed above for negative peel-apart elements. The photorelease layeris about 0.05 microns to 0.2 microns thick. The preferred oxyethylenehomopolymer is polyethylene oxide of molecular weight 100,000 to600,000. The preferred coversheet is untreated polyethyleneterephthalate film. Addition of the photorelease layer to the elementreverses the normal peel-apart behavior. The non-polymerized areasadhere to the coversheet and the polymerized areas adhere to theelastomeric layer.

A process for reversing the normal peel-apart behavior of conventionalpeel-apart photosensitive elements is disclosed in co-assigned U.S. Pat.No. 07/391,785, filed Aug. 4, 1989. In this process the coversheet isremoved and the element, minus the coversheet, imagewise exposed toactinic radiation in the conventional manner. Then the coversheet isrelaminated to the element and the element, with the relaminatedcoversheet, overall exposed to actinic radiation and peeled-apart in theconventional manner. The areas which were not exposed during imagewiseirradiation adhere to the coversheet and are removed, uncovering theelastomeric layer, which may then be toned in an imagewise manner.

Solvent-Processible, Tonable Photosensitive Elements

Solvent-processible, tonable photosensitive elements comprise aphotosensitive layer, an elastomeric layer, and a support. In theseelements the photosensitive layer is either photosolubilizable, that is,after exposure to actinic radiation it becomes soluble in the processingsolvent, or photoinsolubilizable, that is, after exposure to actinicradiation it becomes insoluble in the processing solvent. If thephotosensitive layer is photosolubilizable, the element is negativeworking. If the photosensitive layer is photoinsolubilizable, theelement is positive working.

Positive Working Solvent-Processible Tonable Elements

Fan, U.S. Pat. No. 4,053,313, discloses positive working, solventprocessible elements. The photosensitive layer is a photohardenablelayer similar to that used in conventional negative working peel-apartphotosensitive elements. Processing is by washing out the unexposedimage areas with an organic solvent. The revealed underlying tonableelastomeric layer may then be toned.

Negative Working Solvent-Processible Tonable Elements

Spechler, U.S. Pat. No. 4,376,158, discloses negative working, solventprocessible elements in which the photosolubilizable layer is anapthaquinone diazide sensitized Novalac® resin. Washout of the exposedimage areas is with aqueous sodium hydroxide. This element has theadditional advantage that the portion of the photosolubilizable layerremaining following exposure and washout is still photoactive. It can beremoved by overall exposure and washout to leave an image consisting oftoned elastomeric layer and support.

Fan, U.S. Pat. No. 4,053,313, discloses negative working, solventprocessible elements. The photosensitive layer is a photohardenablelayer similar to that used in conventional negative working peel-apartphotosensitive elements except that a nitroaromatic photoinhibitor isused to reverse the normal behavior of the photohardenable layer.Nitroaromatic photoinhibitors and their process of use are disclosed inPazos, U.S. Pat. No. 4,269,933 and Dueber and Nebe, U.S. Pat. No.4,477,556. In this case the photosensitive layer isphotoinsolubilizable, but the element is positive working because thenitroaromatic photoinhibitor reverses the normal behavior of theelement.

Exposure/Image Formation

Any convenient source providing actinic radiation absorbed by thephotoactive agent present in the element may be used to expose any ofthe elements herein described. The "photoactive agent" is the species,or group of species, which absorb light and initiate the photoimagingreaction. "Actinic radiation" is any radiation which initiates thephotosensitive reaction. The radiation can be natural or artificial,monochromatic or polychromatic, incoherent or coherent. For efficientimage formation most of the actinic radiation should be absorbed by thephotoactive agent. Conventional sources of actinic radiation includefluorescent, mercury vapor, mercury-xenon, metal additive, and arclamps. Useful sources of coherent radiation are lasers whose emissionsfall within or overlap the absorption bands of the photoactive agent.

Exposure is conventionally carried out through an image-bearingtransparency, preferably a half-tone or continuous-tone color separationtransparency. However, other means, such as a modulated scanning laserbeam, CRT (cathode ray tube), and the like, are alternative ways ofimagewise exposing the elements and are considered to be equivalent.However, if sources such as these are used, special means of invertingthe image (i.e., creating a mirror image exposure) would have to bedevised. It would be necessary to invert the image electronically, inthe case of, for example, an electronic imaging system, or to expose thenon-colored, tonable element in the inverted position as describedabove. Such processes are considered equivalent to inverting thetransparency.

Following exposure and processing, the element is colored by applying asuitable colorant, generally know as a toner. After the excess toner isremoved, toner will remain only on the exposed image areas, in the caseof negative working elements, or unexposed image areas, in the case ofpositive working elements. Suitable toners are described in Chu et al.,U.S. Pat. No. 3,620,726; Gray, U.S. Pat. No. 3,909,282; Manger et al.,U.S. Pat. No. 4,215,193; and Ruskin, U.S. Pat. No. 4,661,439. Toners maybe applied by dusting with pads dipped in toners (Burg et al., U.S. Pat.No. 3,060,024); transfer (Burg et al., U.S. Pat. No. 3,060,025);hand-operated machine toning (Sandner, U.S. Pat. No. 4,019,821); andautomatic toning (Tobias, U.S. Pat. No. 4,069,791).

Precolored Overlay Proofing Systems

Any conventional precolored overlay proofing film, or combinationthereof, may be used in the process of this invention. Overlay systemsvary considerably as to their structure and chemical composition, buteach provides a colored image on a relatively clear, dimensionallystable transparent film. Commercially available overlay color proofingfilms include: Cromacheck® (Du Pont, Wilmington, DE), Color Key® (3M,St. Paul, MN), and NAPS and PAPS (Enco Printing Products, Somerville,NJ). These systems are described in detail in Principles of ColorProofing, by Michael H. Bruno, GAMA Communications, Salem, NH, 1986,Chapter V, "Off-Press Color Proofing Systems--Overlay", pp 133-146, theteachings of which are incorporated by reference.

Cromacheck® overlay color proofing film is a totally dry,negative-working, precolored overlay color proofing film. Images areproduced by exposure and peeling-apart of the exposed film. Each filmcomprises a photosensitive layer comprising an ultraviolet-sensitivephotopolymer composition containing an appropriate process colorpigment. This layer is protected on the top and bottom by polymer films.Exposure changes the characteristics of the photopolymer so that theexposed areas adhere to the top film when the films are peeled apart.This top film with its adherent colored image areas becomes the negativeoverlay image. Cromacheck® overlay color proofing film is similar instructure and composition to the peel-apart photosensitive elementsdescribed in Taylor, U.S. Pat. No. 4,489,154, the disclosure of which isincorporated by reference.

Color Key® overlay color proofing film is a solvent-processible,negative-working, precolored proofing film. The film comprises a diazolight sensitive coating covered by a pigmented lacquer. Exposure changesthe solubility of the exposed light-sensitive layer so that it and theoverlying pigment layer is removed during solvent processing.

NAPS and PAPS are, respectively, negative-working and positive-workingprecolored overlay proofing films. Dye sensitized coatings are usedinstead of pigments. Processing is by washout.

Industrial Applicability

The process of this invention are useful for preparing colored images.These images are particularly useful in the graphic arts field,especially in the area of color proofing, wherein proofs are prepared toduplicate the images produced by printing.

The advantageous properties of this invention can be observed byreference to the following examples which illustrate, but do not limit,the invention.

EXAMPLES

    ______________________________________                                        GLOSSARY                                                                      ______________________________________                                         -o-Cl-HABI   1,1'-Biimidazole, 2,2'-bis [ -o-chloro-                                       phenyl]-4,4',5,5'-tetraphenyl-; CAS                                           1707-68-2                                                       Elvacite ® 2051                                                                         Poly(methyl methacrylate); MW                                                 350,000; E. I. duPont deNemours and                                           Company, Wilmington, DE                                         Gentro ® 1506/27                                                                        Styrene-butadiene random copolymeric                                          rubber; Gen Corp., Akron, OH                                    Irganox ® 1010                                                                          Tetra-bis methylene 3-(3,5-di-tert-                                           butyl-4-hydroxyphenyl) propionate                                             methane; Ciba-Geigy, Hawthorne, NY                              2-MBO         2-Mercaptobenzoxazole; 2-                                                     Benzoxazolethiol; CAS 2382-96-9                                 Novacure ® 3704                                                                         Methacrylate ester of the                                                     epichlorohydrin adduct of bis-phenol A;                                       Rad-Cure, Louisville, KY                                        Polyox ® WSRN 3000                                                                      Polyethylene oxide, MW 400,000; Union                                         Carbide, Danbury, CT                                            Taktene ® CB221                                                                         Poly (cis-butadiene); B. F. Goodrich,                                         Cleveland, OH                                                   Tinopal ® PCR                                                                           2-(Stibyl-4")-(naphtho-1',2',4,5)-1,2,3-                                      triazol-2"-sulfonic acid phenyl ester;                                        Benzenesulfonic acid, 5-(2H-                                                  naphtho<1,2-D>triazole-2-yl)-2-(2-                                            phenylethyl)-, phenyl ester; CAS 6994-                                        51-0; Ciba-Geigy, Hawthorne, NY                                 Tinopal ® SFG                                                                           3-Phenyl-7-[2'-(4'-N,N-diethylamino-6'-                                       chloro-1',3',5'-triazinylamino]-coumarin;                                     Ciba-Geigy, Hawthorne, NY                                       Tinuvin ® 328                                                                           2-(2'-Hydroxy-3',5'-di-tert-                                                  amylphenyl)-benzotriazole; Ciba-Geigy,                                        Hawthorne, NY                                                   ______________________________________                                    

EXAMPLE 1

This example illustrates the preparation of a multicolored overlay proofusing overlay images formed from commercial precolored overlay proofingfilm combined with images formed from non-colored, tonable elements. Theassembled overlay proof contains seven images, as represented by a setof seven negative separation transparencies of the original image to bereproduced. The yellow, magenta, cyan, and black separationtransparencies are conventional half-tone color separationtransparencies. The gold, silver, and bronze transparencies areconventional continuous tone transparencies. The yellow, cyan, and blackimages were prepared from commercial precolored overlay proofing films.The magenta, silver, gold, and bronze images were prepared by toningnon-colored, tonable photohardenable elements.

The precolored films are commercial Cromacheck® overlay color proofingfilms, similar in composition, structure, and method of manufacture tothose disclosed in Example 1 of U.S. Pat. No. 4,489,154.

To prepare the non-colored, tonable photohardenable elements, thephotohardenable layer described below was coated on an about 13micrometer (0.5 mil) thick clear polyethylene terephthalate coversheetwhich has been surface treated with an electric discharge of about 0.544coulomb/m² (22.5% solids from 96:4 dichloromethane/methanol solventsystem) at a coating weight of about 40 mg/dm². The elastomeric layer is79.5% Taktene® 221, 20.0% Gentro® 1506, and 0.5% of Irganox® 1010,coated on the support (7.7% solids from dichloromethane solvent) atabout 125 mg/dm². The support is an about 50 micron (2 mil) thick clearpolyethylene terephthalate film. The photohardenable layer and theelastomeric layer were laminated together at room temperature and about40 pounds per in² pressure to form a non-colored, tonablenegative-working, peel-apart overlay element.

                  TABLE 1                                                         ______________________________________                                        COMPOSITION OF THE NON-COLORED                                                PHOTOHARDENABLE LAYER.sup.a                                                   ______________________________________                                        Elvacite ® 2051                                                                             43.51                                                       Novacure ® 3704                                                                             49.49                                                        -o-Cl HABI       2.50                                                        2-MBO             1.50                                                        Tinopal ® PCR 0.50                                                        Tinopal ® SFG 1.50                                                        Tinuvin ® 328 0.20                                                        Polyox ® WSRN 3000                                                                          0.50                                                        ______________________________________                                         .sup.a in percent                                                        

STEP 1

A sheet of yellow Cromacheck® overlay color proofing film was placed ina vacuum frame with the coversheet up, i.e. facing the light source. Theyellow half-tone negative separation transparency was placed on top ofthe coversheet with the emulsion side in contact with the coversheet andthe base side up. A vacuum was drawn on the element and separationtransparency for 90 sec prior to exposure. The element was exposed forabout 36 sec with the radiation from an unfiltered 5 kw high pressuremercury vapor lamp (Violux® 5002S, Exposure Systems Company, Bridgeport,CT, equipped with a photopolymer bulb) about 54 in (137 cm) above theelement and separation transparency. The exposed precolored film wasremoved from the vacuum frame and placed on a vacuum easel. The clearpolyethylene terephthalate coversheet was removed by peeling back at180° ("peel-back mode") in a smooth, continuous motion. A yellow overlayimage was produced on the coversheet. Correct left to right orientationvis-a-vis the original is achieved by viewing the image through thetransparent coversheet, with the colored image on the side away from theviewer.

STEP 2

A non-colored, tonable photosensitive element was placed in a vacuumframe with the coversheet up. The magenta half-tone negative separationtransparency was placed on top of the coversheet in the invertedposition, i.e., with the emulsion side up and the base side in contactwith the coversheet. A vacuum was drawn on the element and separationtransparency for 90 sec prior to exposure. The element was exposedthrough the inverted magenta negative separation transparency asdescribed in Step 1. The exposed non-colored, tonable element wasremoved from the vacuum frame and placed on a vacuum easel. The clearpolyethylene terephthalate coversheet was removed by peeling back at180° ("peel-back mode") in a smooth, continuous motion. The uncoveredareas of the elastomeric layer were toned with Du Pont negativeCromalin® FP 1 fluorescent pink toner using conventional hand toningtechniques. A toned magenta overlay image which is a negative of theseparation transparency, was produced on the transparent support. Thisimage was inverted (i.e., turned over so that the support was "up",i.e., facing the observer, and the toned side was "down", i.e., awayfrom the observer) to produce a magenta overlay image with the correctleft to right orientation. This image was stacked in register with theprecolored overlay image produced in Step 1 to produce a two coloroverlay proof containing a precolored image and a toned image, both ofwhich have the correct left to right orientation.

STEP 3

A sheet of cyan Cromacheck® overlay color proofing film was placed in avacuum frame with the coversheet up, i.e. facing the light source. Thecyan half-tone negative separation transparency was placed on top of thecoversheet with the emulsion side in contact with the coversheet and thebase side up. The element was exposed and peeled-apart as described inStep 1 to produce a cyan overlay image on the coversheet. This image wasstacked in register with the images produced in the preceding steps toproduce a three color overlay proof containing two precolored images anda toned image, all of which have the correct left to right orientation.

STEP 4

A non-colored, tonable photosensitive element was placed in a vacuumframe with the coversheet up. A silver continuous tone negativeseparation transparency was placed on top of the coversheet in theinverted position, i.e., with the emulsion side up and the base side incontact with the coversheet. The element was exposed, peeled-apart,toned with MS1 metallic silver toner, and inverted as described in Step2 to produce a silver overlay image with the correct left to rightorientation. This image was stacked in register with the images producedin the preceding steps to produce a four color overlay proof containingtwo precolored images and two toned images, all of which have thecorrect left to right orientation.

STEP 5

A non-colored, tonable photosensitive element was placed in a vacuumframe with the coversheet up. The gold continuous tone negativeseparation transparency was placed on top of the coversheet in theinverted position, i.e., with the emulsion side up and the base side incontact with the coversheet. The element was exposed, peeled-apart,toned with MG3 metallic gold toner, and inverted as described in Step 2to produce a gold overlay image with the correct left to rightorientation. This image was stacked in register with the images producedin the preceding steps to produce a five color overlay proof containingtwo precolored images and three toned images, all of which have thecorrect left to right orientation.

STEP 6

The non-colored, tonable photosensitive element was placed in a vacuumframe with the coversheet up. The copper continuous tone negativeseparation transparency was placed on top of the coversheet in theinverted position, i.e., with the emulsion side up and the base side incontact with the coversheet. The element was exposed, peeled-apart,toned with MB1 metallic copper toner, and inverted as described in Step2 to produce a copper overlay image with the correct left to rightorientation. This image was stacked in register with the images producedin the preceding steps to produce a six color overlay proof containingtwo precolored images and four toned images, all of which have thecorrect left to right orientation.

STEP 7

A sheet of black Cromacheck® overlay color proofing film was placed in avacuum frame with the coversheet up, i.e., facing the light source. Theblack half-tone negative separation transparency was placed on top ofthe coversheet with the emulsion side in contact with the coversheet andthe base side up. The element was exposed and peeled-apart as describedin Step 1 to produce a conventional black overlay image. This image wasstacked in register with the images produced in the preceding steps toproduce a seven color overlay proof containing three precolored overlayimages and four toned overlay images, all of which have the correct leftto right orientation.

EXAMPLE 2

This example illustrates the preparation of a multicolor overlay proofusing images formed from a different commercial precolored overlayproofing film combined with an image formed from a non-colored, tonableelement. The overlay proof contains five images. The yellow, magenta,cyan, and black images were prepared from commercial precolored overlayproofing films. The gold image was prepared by toning a non-colored,tonable photohardenable element.

A set of four color overlay images was prepared as directed by themanufacturer from a set of four conventional half-tone negativeseparation transparencies using NAPS (Enco Printing Products,Somerville, NJ) negative overlay color proofing films colored yellow,magenta, cyan, and black. Exposure was carried out as prescribed by themanufacturer, i.e., in a vacuum frame with the emulsion side of thenegative in contact with the emulsion side of the overlay proofing filmand the base of the transparency facing the source of actinic radiation.The overlay films are each viewed as exposed with the emulsion side up,facing the viewer, to achieve the correct left to right orientation.

A gold, toned overlay image was formed following the procedure ofExample 1, Step 2. The non-colored, tonable photosensitive elementdescribed in Example 1 was placed in a vacuum frame with the coversheetup. A gold continuous tone negative separation transparency was placedon top of the coversheet in the inverted position, i.e., with theemulsion side facing the source of actinic radiation and the base sidein contact with the coversheet. A vacuum was drawn on the element andseparation transparency. The element was exposed, peeled-apart, andtoned with a conventional Du Pont Cromalin® metallic gold toner. Thetoned gold overlay image was then inverted, as described in Example 1,Step 2, and assembled in register with the four precolored overlayimages, to produce a five-color, five-layer overlay proof.

EXAMPLE 3

This example illustrates the preparation of a multicolor overlay proofusing images formed from yet a different commercial precolored overlayproofing film combined with an image formed from a non-colored, tonableelement. The overlay proof contains five color separation images. Theyellow, magenta, cyan, and black images were prepared from commercialprecolored overlay proofing films. The silver image was prepared bytoning a non-colored, tonable photohardenable element.

A set of four color overlay images was prepared as directed by themanufacturer from a set of conventional halftone negative separationtransparencies using Color Key® (3M, St. Paul, MN) negative overlaycolor proofing films colored yellow, magenta, cyan and black. Exposurewas carried out as prescribed by the manufacturer, i.e., in a vacuumframe with the emulsion side of the negative in contact with the overlayproofing film and the base facing the source of actinic radiation. TheColor Key film is placed in the vacuum with the pigmented photosensitivecoating facing away from the light source. The processed overlay imagesare also assembled and viewed with the image side down, facing away fromthe viewer.

A silver, toned overlay image was formed following the procedure ofExample 1, Step 2. A non-colored, tonable photosensitive element asdescribed in Example 1 was placed in a vacuum frame with the coversheetup. A silver continuous tone negative separation transparency was placedon top of the coversheet in the inverted position, i.e., with theemulsion side facing the source of actinic radiation and the base sidein contact with the coversheet. A vacuum was drawn on the element andseparation transparency. The element was exposed, peeled-apart, andtoned with a Du Pont Cromalin® metallic silver toner.

The silver, toned overlay image was inverted as described in Example 1,Step 2, to produce a silver overlay image with the proper left to rightorientation. The five overlay images were stacked in register on areceptor of heavy white paper to produce a five color overlay imageconsisting of, in order from bottom to top: receptor, yellow precoloredoverlay image, magenta precolored overlay image, cyan precolored overlayimage, black precolored overlay image, and silver toned overlay image.

Although the foregoing disclosure is believed sufficient to permit thoseskilled in the art to fully understand and practice the invention, anumber of patents and other references cited in the specification areconsidered valuable sources of additional information. These citedmaterials are hereby incorporated by reference.

What is claimed is:
 1. A multilayer, multicolor overlay proof comprisinga toned overlay image and a precolored overlay image prepared by:(A)providing at least two different conventional color separationtransparencies of the image to be reproduced, all of which are eitherpositive or negative, and each comprising an emulsion image on a base;(B) providing at least one precolored photosensitive overlay element andat least one non-colored, tonable photosensitive element, all of whichare either positive or negative working as required by said separationtransparencies, said non-colored, tonable photosensitive elementcomprising, in order, a photosensitive layer, an elastomeric layer, anda transparent support; (C) exposing a precolored photosensitive overlayelement to actinic radiation through its corresponding color separationtransparency with the emulsion side of the transparency down, anddeveloping to provide a precolored overlay image; (D) exposing anon-colored, tonable photosensitive element through a different colorseparation transparency with the emulsion side of the transparency up,developing and toning with a correspondingly colored toner to provide atoned overlay image, and inverting said toned overlay image to obtainthe correct left to right orientation; and (E) assembling in register,said developed precolored overlay image in exposure position and saiddeveloped toned overlay image in inverted position to form a multilayer,multicolor overlay proof with correct left to right orientation;whereinsteps (C) and (D) may be carried out in either order.
 2. A proof ofclaim 1 wherein said non-colored, tonable photosensitive element is apeel-apart element comprising, in order, a coversheet, a photohardenablephotosensitive layer, an elastomeric layer, and a transparent support.3. A proof of claim 2 wherein said peel-apart element is negativeworking.
 4. A proof of claim 3 additionally comprising one or moreprecolored overlay images and/or toned overlay images.
 5. A proof ofclaim 3 comprising a precolored overlay image colored yellow, magenta,cyan, or black.
 6. A proof of claim 4 comprising precolored overlayimages colored yellow, magenta, cyan, and black.
 7. A proof of claim 2wherein said peel-apart element is positive working.
 8. A proof of claim7 wherein said peel-apart element additionally comprises a photoreleaselayer between said coversheet and said photohardenable photosensitivelayer.
 9. A proof of claim 1 wherein said non-colored, tonablephotosensitive element is a solvent-processible element comprising, inorder, a solvent-processible photosensitive layer, an elastomeric layer,and a transparent support.
 10. A proof of claim 9 wherein saidsolvent-processible element is negative working.
 11. A proof of claim 9wherein said solvent-processible element is positive working.
 12. Aproof of claim 11 wherein said positive-working solvent-processibleelement comprises a photohardenable photosensitive layer.
 13. Amultilayer, multicolor overlay proof comprising a toned overlay imageand a precolored overlay image prepared by:(A) providing at least twodifferent conventional color separation transparencies of the image tobe reproduced, all of which are either positive or negative, and eachcomprising an emulsion image on a base; (B) providing at least oneprecolored photosensitive overlay element and at least one non-colored,tonable photosensitive element, all of which are either positive ornegative working as required by said separation transparencies, saidnon-colored, tonable photosensitive element comprising a photosensitivelayer on a transparent support; (C) exposing a precolored photosensitiveoverlay element to actinic radiation through its corresponding colorseparation transparency with the emulsion side of the transparency down,and developing to provide a precolored overlay image; (D) exposing anon-colored, tonable photosensitive element through a different colorseparation transparency with the emulsion side of the transparency up,developing and toning with a correspondingly colored toner to provide atoned overlay image, and inverting said toned overlay image to obtainthe correct left to right orientation; and (E) assembling in register,said developed precolored overlay image in exposure position and saiddeveloped toned overlay image in inverted position to form a multilayer,multicolor overlay proof with correct left to right orientation;whereinsteps (C) and (D) may be carried out in either order.
 14. A proof ofclaim 12 wherein said non-colored, tonable photosensitive overlayelement is positive working.
 15. A proof of claim 14 wherein saidnon-colored, tonable photosensitive overlay element comprises aphotosensitive layer which is photohardenable.
 16. A proof of claim 13wherein said non-colored, tonable photosensitive overlay element isnegative working.
 17. A proof of claim 16 wherein said non-colored,tonable photosensitive overlay element comprises a photosensitive layerwhich is phototackifiable.